Weston-Simons J S, Kendrick B J L, Mentink M J A, Pandit H, Gill H S, Murray D W
Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Windmill Road, Headington, Oxford, OX3 7LD, UK.
Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Windmill Road, Headington, Oxford, OX3 7LD, UK.
Knee. 2014 Jan;21(1):304-9. doi: 10.1016/j.knee.2013.04.008. Epub 2013 May 12.
The Oxford Unicompartmental Knee Replacement (OUKR) uses a mobile bearing to minimise wear. Bearing dislocation is a problem in the lateral compartment as the ligaments are loose in flexion. A domed tibial component has been introduced to minimise the risk of dislocation, yet they still occur, particularly medially. The aim of this mechanical study was to compare the domed and flat tibial components and to identify surgical factors that influence the risk of dislocation.
A jig was constructed to assess the amount of vertical distraction of the lateral OUKR for a dislocation to occur. Three methods of dislocation were assessed: laterally, medially, 'over the wall' and anteriorly. The study focused on medial dislocation.
Significantly (p=0.02) greater vertical distraction was required to dislocate the bearing with the domed tibia rather than the flat. For medial dislocation bearing distance from the wall, femoral component external rotation and tibial rotation were associated with significantly less distraction for dislocation. With the optimal technique with the domed tibia the distraction required to dislocate the bearing medially was 6.4 mm, whereas with poor technique it was 4.6 mm.
This study suggests that to minimise the risk of dislocation the domed tibia should be used. The component should be implanted so the bearing is close to the wall, but does not hit it, and in flexion the femoral and tibial components should be neutrally aligned.
牛津单髁膝关节置换术（OUKR）采用活动衬垫以减少磨损。由于外侧间室的韧带在屈曲时较为松弛，衬垫脱位是一个问题。已引入圆顶形胫骨部件以降低脱位风险，但脱位情况仍会发生，尤其是在内侧。本力学研究的目的是比较圆顶形和平面形胫骨部件，并确定影响脱位风险的手术因素。
构建一个夹具，以评估外侧OUKR发生脱位时的垂直牵开量。评估了三种脱位方式：外侧、内侧、“越过骨壁”和前方。该研究重点关注内侧脱位。
与平面形胫骨相比，圆顶形胫骨使衬垫脱位所需的垂直牵开量显著更大（p = 0.02）。对于内侧脱位，衬垫与骨壁的距离、股骨部件的外旋和胫骨的旋转与脱位所需的牵开量显著减少相关。采用圆顶形胫骨的最佳技术时，使衬垫内侧脱位所需的牵开量为6.4毫米，而技术不佳时为4.6毫米。
本研究表明，为将脱位风险降至最低，应使用圆顶形胫骨。植入部件时应使衬垫靠近骨壁，但不接触骨壁，并且在屈曲时股骨和胫骨部件应呈中立对齐。
